Anthony J. Garcia, 40, of Terre Haute, Ind., was arrested Monday during a traffic stop on Interstate 57 in southern Illinois after a task force worked for almost two months to find the link between the 2008 deaths of a Creighton University professor's son and their housekeeper and the recent deaths of another Creighton University professor and his wife.

According to an affidavit, detectives found "significant similarities" between the killings.

Investigators poured over Creighton University School of Medicine files and found that one student -- Anthony J. Garcia -- had been terminated by the professor killed in 2013 and the father of the boy killed in 2008.

Drs. Roger Brumback and Bill Hunter both served as leaders for Creighton University's pathology department at the time that Garcia's residency in that department was terminated in 2001. In a letter explaining the decision to Garcia, the department referenced an incident in which Garcia made a phone call to a fellow resident while the colleague was taking a high-stakes examination.

For the next several years, documents supporting Garcia's medical licensing applications reveal, the suspected killer tried unsuccessfully to obtain medical licences in various states.

Investigators noted numerous requests for verification of Garcia's attendance in the program from various institutions. Each time, both Drs. Brumback and Hunter responded to the request by documenting his unsuccessful completion of the program.

Just 13 days before the 2008 deaths of Thomas Hunter, 11, and Shirlee Sherman, 57, Garcia was sent a notification indicating he would likely be denied a medical license in Louisiana.

"You may not possess the necessary qualifications for medical licensure and are therefor ineligible for consideration," the notice read.

That notice indicated that Garcia did not inform the Louisiana State Board of Medical Examiners that he did not complete his pathology internship program at Creighton.

The affidavit reveals Garcia had a silver 2000 Honda CRV registered to him at the time of the 2008 killings. That was the vehicle described in FBI posters seeking information about the case. Further, witnesses noted an olive-skinned man between 20 and 40 walking through the Dundee neighborhood at the time of the murders.

A few months after Hunter and Sherman were found dead in their Dundee home, Garcia applied for but failed to obtain a medical license in Indiana. The board there reasoned that its recommended denial was based on Garcia's failure to complete residency programs at various schools. Instead of being denied, Garcia withdrew his application.

Garcia tried once more in 2012 to obtain an Indiana medical license. This time, a letter confirming Garcia's residency status at Creighton written by Brumback specifically mentions the phone call incident and says Garcia was asked to resign or face termination.

The Medical Licensing Board of Indiana again recommended denying Garcia an application, but he withdrew it after learning of his fate in late 2012.

In phone records obtained by police as they worked the case, an incoming call to his phone placed him near Atlantic, Iowa, on May 12, 2013. In surveillance images released by police late Wednesday night, Garcia is seen at a Council Bluffs, Iowa, convenience store making a purchase the same day -- two days before the Brumbacks were found dead in their home.

Police said they found documentation that Garcia had purchased a Smith & Wesson 9mm handgun from a store in Indiana just two months prior. Broken pieces and a magazine found at the scene of the Brumback homicides were consistent with the handgun purchased, the affidavit said.

Garcia faces eight felony counts -- four for first-degree murder, three for use of a weapon to commit a felony and one for use of a firearm to commit a felony.

He waived extradition in Union County, Ill., court on Wednesday. He's expected to be returned to Omaha within the next couple of weeks.